Renaming files outside of MC is not the best idea. When you do this, it is as if you deleted the files and then added new ones.
The right way to rename files or folders is to use MC to do it. MC's Rename, Move, and Copy Files tool (RM&C) can do all of these types of tasks and do them correctly.
https://wiki.jriver.com/index.php/Rename,_Move,_and_Copy_FilesWhen you use MC to do the renames, it knows which files moved where so the database stays consistent: All of your tags stay the same including import date and all other custom tags you have defined, set, etc.
On occasion I do huge moves of my collection. Usually things like moving my entire music folder from one drive to another. In that example (moving from one drive to another) all of the structure stays the same, but the front part of the path (the drive letter) changes.
In a case like this, I'll use an external tool to move the files, as moving gigabytes of data is not a good task for MC. When I'm done with the move, I *inform* MC about my change by using RM&C. Inside RM&C there is a mode called "update database only". Using that tool I can tell MC that I've changed file paths, select the files, select the paths to substitute and then press "OK". It only takes a blink of an eye and MC has updated all of the paths to be correct.
RM&C is one of MC's best and most powerful features. It will allow you to move your collection around on drives, copy your collection to new computers, rename subsets of your collection, and more. Learn this tool and your mastery of MC will increase by several levels!
Best of luck.
Brian.